Item Category

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Create an Item Category when several Item Definitions need the same structure, inherited attributes, UI treatment, Item Actions, or inventory restrictions. Build categories before definitions so every new definition immediately receives the correct fields and behavior mappings.

Create the starter category structure

  1. Open Tools > Opsive > Ultimate Inventory System > Main Manager.
  2. In Setup, confirm that the intended Inventory System Database is selected.
  3. Open Item Categories.
  4. Select the existing All category and review its common Item Definition attributes, including Icon and Description.
  5. Enter Consumable beside Add, create it, and add All to Parents.
  6. Create Equippable and add All to Parents.
  7. Create Weapon and add Equippable to Parents.

The resulting hierarchy is:

  • All
    • Consumable
    • Equippable
      • Weapon

Use Consumable for Health Potion. Use Weapon for Iron Sword and Fire Wand so both definitions also inherit from Equippable and All.

The Item Category editor showing the category list and the selected category's Properties, Attributes, and Relationships sections.

Choose category properties

The Properties section controls decisions that apply to Items whose definitions directly use the category.

Property Choose it when Standard example
Name The category needs a unique project name. The Scriptable Object filename follows it. Weapon
Mutable Runtime Items must change their own Item attribute values. Weapon Items with changing Durability
Unique Items must retain individual identity and should not stack in the default Item Collection. Individual Iron Sword and Fire Wand Items
Abstract The category exists only to organize or share data and should not be selectable by Item Definitions. All or Equippable, when definitions always use narrower categories
Editor Color A large database needs a visual grouping aid. One color for equipment-related categories
Editor Icon The category needs an explicit editor icon instead of the CategoryIcon attribute fallback. A weapon-category icon
Parents The category should inherit declarations or mappings from another category. Weapon inherits from Equippable

For the standard sample, leave Consumable Mutable and Unique disabled when matching Health Potion Items should stack and do not have per-instance changing values. Enable both on Weapon when each Iron Sword or Fire Wand must keep its own changing Durability.

Be cautious with mutable, common Items: when matching Items merge in an Item Collection, one instance’s Item attribute values can be lost. Use Unique when individual runtime values must be preserved.

Decide between one parent and multiple parents

Use a single parent when the category hierarchy already expresses the relationship. Weapon needs Equippable as its parent; it does not also need All because Equippable already inherits from All. Do not make Weapon inherit Consumable simply to reuse one value—move that shared declaration to All instead.

Multiple parents are useful only when a category genuinely combines independent capabilities. Before adding another parent, confirm that:

  • The new parent is not a descendant of the selected category, which would create a loop.
  • Same-named inherited attributes use the same type. Parents with same-named attributes of different types overlap and cannot be combined safely.
  • The parent order is intentional. When multiple parents supply the same name and type, inheritance uses the first parent containing that attribute.

Use the Relationships section to review Ancestors and Descendants after changing parents.

Declare attributes in the correct collection

The Item Category editor is the only place where attributes can be added or removed. The Attributes section has three tabs:

Tab What it declares Standard example
Item Category Values that describe a category and can be inherited by child categories CategoryIcon
Item Definition Fields whose values are set per definition Icon, Description, BuyPrice, and Weapon-only Attack
Item Fields whose values can differ between runtime instances Weapon-only Durability

Keep Icon, Description, and BuyPrice on All when every definition needs them. Add Attack to Weapon’s Item Definition tab and Durability to Weapon’s Item tab. Iron Sword and Fire Wand then receive the weapon fields, while Health Potion does not.

Use + to add a declaration and – to remove one. Removing an inherited declaration can affect parent and child categories, definitions, and Default Item values, so review the removal prompt and the Relationships section before confirming it.

Use categories in actions, equipment, and UI

Creating a category does not automatically create its downstream mappings. Configure the systems that consume it:

  • In a Category Item Action Set, map a Consume action to Consumable and an Equip action to Equippable or Weapon. The Item View Slots Container binding then finds the actions that match the selected Item’s categories.
  • In an Item Slot Set, restrict a weapon slot to Weapon. A Right Hand slot with a size limit of 1 then accepts one Iron Sword or Fire Wand but rejects Health Potion.
  • In a Category Item View Set, map Consumable or Weapon to a different Item View prefab only when those categories need different presentation.

Prefer the broadest category that accurately describes the behavior. Map Equip to Equippable when every equippable Item should receive it; map a weapon-only action to Weapon.

Find and review categories

Use the search field when the category list becomes large:

  • c:<CategoryName> finds categories with that direct parent.
  • i:<CategoryName> finds categories that inherit from that ancestor.
  • a:<AttributeName> finds categories containing that attribute.

The Relationships section provides navigation to Ancestors, Descendants, Direct Item Definitions, Inherited Item Definitions, Direct Recipes, and Inherited Recipes. Select the colored box beside a related object to open it.

Right-click a Category row and choose Duplicate when a new Category should begin with the same mutable/unique/abstract settings, parents, Attribute declarations, and values. The duplicate is a new Category identity with a generated name; existing Definitions stay assigned to the original. Rename it, review every copied Attribute family, and assign Definitions deliberately.

Editor checkpoints

Before creating more definitions, confirm that:

  • Consumable and Equippable show All as their direct parent.
  • Weapon shows Equippable as its direct parent and All as an ancestor.
  • Health Potion uses Consumable; Iron Sword and Fire Wand use Weapon rather than Uncategorized.
  • All supplies the common Item Definition fields, while Weapon alone declares Attack and Durability in the intended tabs.
  • Consumable is common and immutable for the stacking sample; Weapon is mutable and unique for per-Item Durability.
  • Abstract is enabled only on categories that definitions should not select directly.
  • Item Action Sets, Item Slot Sets, and Category Item View Sets reference the intended broad or narrow category.

Verify in Play Mode

  1. Add a stack of Health Potion Items and two Iron Sword Items to the player’s Bag collection.
  2. Confirm that matching Health Potion Items stack when the collection permits stacking.
  3. Change the Durability of one Iron Sword and confirm that the other keeps its own value.
  4. Open the inventory action list and confirm that Health Potion receives its Consumable actions while Iron Sword receives its equipment or weapon actions.
  5. Equip Iron Sword and confirm that the Weapon slot accepts it.
  6. Try to move Health Potion into the Weapon slot and confirm that the Item Slot Set restriction rejects it.

Troubleshooting

  • A category is missing from the Item Definition category field: Check whether Abstract is enabled. Disable it only if definitions should directly use that category.
  • A parent cannot be assigned: Check for a descendant loop and same-named inherited attributes with conflicting types, then fix the hierarchy or move the shared declaration.
  • A definition is missing an attribute: Check its direct Item Category, ancestors, and the tab where the declaration was added.
  • Weapon Items stack or share changing values: Enable Mutable and Unique on the direct Weapon category and keep changing values in the Item attribute collection.
  • Health Potion does not stack: Check that Consumable is not Unique and that the destination Item Collection allows stacking.
  • The wrong Item Actions appear: Check the categories and exclusions on each Item Action Set, then confirm the Category Item Action Set binding used by the UI.
  • An Item cannot enter an equipment slot: Check the Item Slot Set’s allowed Item Category and confirm that the definition inherits from it.